diff --git a/simulations/airshower_beacon_simulation/ab_modify_clocks.py b/simulations/airshower_beacon_simulation/ab_modify_clocks.py
index 1532cdd..eedf05f 100755
--- a/simulations/airshower_beacon_simulation/ab_modify_clocks.py
+++ b/simulations/airshower_beacon_simulation/ab_modify_clocks.py
@@ -26,6 +26,7 @@ if __name__ == "__main__":
     parser.add_argument('-s', '--seed', type=int, nargs='?', default=None, help='Fix seed if supplied.')
     parser.add_argument('--uniform', action='store_const', const='uniform', dest='dist_type')
     parser.add_argument('--gaussian',   action='store_const', const='gauss', dest='dist_type')
+    parser.add_argument('-r','--read-clocks-file', action='store_true', dest='read_clocks_file')
     parser.set_defaults(dist_type='gauss')
 
     parser.add_argument('--data-dir', type=str, default="./data", help='Path to Data Directory. (Default: %(default)s)')
@@ -62,7 +63,11 @@ if __name__ == "__main__":
 
         N_antennas = len(group.keys())
 
-        if True:
+        if args.read_clocks_file and path.isfile(clocks_fname): # read clock deviations from file
+            print(f"Reading clocks from {clocks_fname}.")
+            clock_offsets = np.loadtxt(clocks_fname)
+
+        elif True: # random clock deviations
             print(f"Modifying clocks upto {max_clock_offset}ns.")
             clock_offsets = np.zeros( N_antennas )
             if args.dist_type == 'uniform': # uniform